Various packages have been proposed and some are presently available for storing, shipping and dispensing viscous materials such a shampoos, conditioners, soaps and other flowable products including other liquids, pastes and the like. Some of these packages include a flexible container having a dispensing closure and when inverted and squeezed, opens a self sealing dispensing valve in the closure at a predetermined threshold pressure to discharge the contents of the container. When the external forces on the container are removed, and the internal pressure in the container is reduced below the predetermined threshold pressure for dispensing, the valve closes. The valve remains closed as long as the threshold pressure is not exceeded.
Self sealing dispensing valves have been disclosed in U.S. Pat. Nos. 4,728,006; 5,271,531 and 5,531,363. Self sealing dispensing valves are also offered commercially by Liquid Molding Systems, Inc. of Midland, Mich. which has been issued U.S. Pat. Nos. 5,213,236; 5,377,877 and 5,409,144.
Furthermore, dispensing closures of the foregoing type are, in most instances, required to render the packages "shippers", in that, product will not inadvertently nor accidentally be dispensed during shipment between the time the container is filled with product to be dispensed to the ultimate purchase and use by a consumer.